Semiconductor optical devices in which a lens is attached integrally to its mounting member by molding have been known, as disclosed, e.g., in Japanese Laid-Open Patent Publication No. H07-218773. (In the case of the semiconductor optical device disclosed in this publication, the mounting member is a pipe.) Traditionally, in the manufacture of semiconductor optical devices, the circumference of the lens is metalized, and the lens is secured to a mounting member of metal by soldering, etc. The technique disclosed in the above publication has an advantage over this conventional technique in that a reduced number of parts and a reduced number of joins are required and hence higher mass productivity can be attained since the lens is attached integrally to the mounting member by molding.
In the case of CAN packages, the lens is mounted to a cylindrical mounting member called a cap. The cap may be formed of a resin, and the lens may be attached integrally to this cap by molding to achieve the same advantages as described in connection with the technique of the above publication. However, unlike metal caps, which are traditionally used, a resin cap cannot be secured to the stem by welding. Therefore, the cap may be bonded to the stem by an adhesive.
In semiconductor optical devices configured as CAN packages, the semiconductor optical element is mounted inside the cap. The semiconductor optical element is either a semiconductor laser diode or a photodiode. The accuracy of the alignment of the lens with the optical axis of the semiconductor optical element is an important factor in determining the performance of the semiconductor optical device. In the alignment process, the lens is positioned relative to the semiconductor optical element so that the lens is spaced a predetermined distance from the semiconductor optical element in the direction of the optical axis of the semiconductor optical element (i.e., Z direction in, e.g., FIG. 1) and oriented perpendicular to the optical axis of the semiconductor optical element (i.e., oriented parallel to X-Y plane in FIG. 1). That is, the cap with the lens integrally attached thereto must be accurately aligned with and secured to the stem.
In order to accomplish this, Japanese Laid-Open Patent Publication No. H07-218773 noted above and Japanese Laid-Open Patent Publication No. 2003-035855 disclose techniques in which a mounting member (cap) with a lens integrally attached thereto and a stem are provided with steps and/or recesses, thereby making it possible to accurately align the mounting member with the stem using these steps and recesses.
Other prior art include Japanese Laid-Open Patent Publication Nos. 2010-183002 and H03-030581.
CAN packages are configured by mounting various components (including optical elements, such as a semiconductor optical element, and electrical parts) in a closely spaced relationship on a stem and then covering and sealing these components with a cap. Since the cap is mounted on the top surface of the stem, the area available on the top surface for mounting components is limited. Further, providing the cap and the stem with steps or recesses for positioning the cap on the stem (as described in connected with the above conventional techniques) requires the use of some area on the stem, thus reducing the area available on the top surface of the stem for mounting components.